Remesh modifier hits cpu instead gpu and crashes
How can I set the GPU for just everything in blender and rule out the cpu?

Actually, most of the algorithm, operation, modifier, complex computing, data handling is done by CPU, not GPU.
Although Rendering can be accelerated by GPU, but those code is rewrite/design for GPU by developer. Migrating any algorithm to GPU instruction can take a lot of effort due to the lack of some ability and the difference of hard structure. Also, only some algorithm will benefit from GPU.
Remeshing is a complex topic in CG, the new method adopted by Blender is not transferred to GPU code for now. There is nothing Blender can do for you, unless you could develop a GPU accelerated Remeshing algorithm for it.
Algorithm and GPU coding is not that easy as you described.